X-ray tube with a rotary anode

ABSTRACT

An X-ray tube wherein the anode is driven by an induction motor and is provided with a focal point, the cathode being directed upon the focal point path, the rotor of the motor being connected with the rotary axle of the anode and being located within the vacuum case, while the stator is located outside of the case, and wherein the case in the part between the rotor and the stator consists of metal. The tube is particularly characterized in that this metal part is a poor conductor of electrical current.

United States Patent [1 1 Haberrecker [111 3,801,846 Apr. 2, 1974 X-RAY TUBE WITH A ROTARY ANODE [75] Inventor: Klaus l-laberrecker,Erlangen,

Germany [73] Assignee: Siemens Aktiengesellschaft, Munich,

Germany 22 Filed: Mar. 15, 1973 21 Appl. No.: 341,484

[30] Foreign Application Priority Data Mar. 17, 1972 Germany 2213184 [52] US. Cl. 313/60 [51] Int. Cl. H0lj 35/10 [581 Field of Search 313/60 [56] References Cited UNITED STATES PATENTS 12/1943 Atlee 313/60 Primary Examinerl-lerman Karl Saalbach Assistant ExaminerDarwin R. Hostetter Attorney, Agent, or F irm- Richards &' Geier V. Alexander Schere [57] t ABSTRACT An X-ray tube wherein the anode is driven by an induction motor and is provided with a focal point, the cathode being directed upon the focal point path, the rotor of the motor being connected with the rotary axle of the anode and being located within the vacuum case, while the stator is located outside of the case, and wherein the case in the part between the rotor and the stator consists of metal. The tube is particularly characterized in that this metal part is a poor conductor of electrical current.

5 Claims, 3 Drawing Figures X-RAY TUBE WITH A ROTARY ANODE This invention relates to an X-ray tube with a rotary anode and having a vacuum case wherein the cathode and the anode are located opposite each other.

X-ray tubes with rotary anodes used in the present X-ray technology have vacuum cases which usually consist of glass. Glass is used since it is well adapted to treatments used in X-ray tube manufacture and since at the same time it provides electrical insulation. However, the manufacture involves the use of trained persons familiar with the treatment of glass.

An object of the present invention is to simplify the making of X-ray tubes and to provide X-ray tubes which can be manufactured by persons who are not familiar with the treatment of glass.

Other objects will become apparent in the course of the following specification. I

In the accomplishment of the objectives of the present invention it was found desirable to make of' metal the part of the tube case located between the rotor and the stator of the tube. In accordance with the present invention this metal is a poor conductor of electrical current. The poor conductivity of I electrical current is to be considered in comparison to that of copper. A poorly conducting material which also has sufficient mechanical stability, is for example, non-magnetic rustfree steel, such as is known under the idication V2A- steel.

X-ray tubes with rotary anodes having a part consisting of metal, which separates the rotor from the stator, can be made with less precision, since this part containing the rotary section of the tube when made of metal does not require the precise manufacture necessary for glass parts. Furthermore, the fixing of the parts to each other can be made in a much more simple way, since attaching means can be used which are generally used in metal constructions. In addition, due to small electrical conductivity the induced electrical output and thus the heat loan remain small during operation.

An X-ray tube is known already the case of which consists to a larger part of metal and wherein the part between therotor and the stator is also of metal. However, in that construction magnetically conducting parts are inserted at the stator poles into the case. The complication of this construction the parts of which must be inserted vacuum tightly, was obviously the reason why the tube which is known for nearly 30 years, has not been used in X-ray practice. The prior tube does not have the recognition of the present invention that it is possible to eliminate magnetically conducting inserts when a metal part of small electrical conductivity is used.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawing showing by way of example only, preferred embodiments of the inventive idea.

In the drawing:

FIG. 1 is a partly sectional view of an X-ray tube with a rotary anode of the usual type, wherein the part containing the rotor consists of metal.

FIG. 2 is a circuit diagram showing electrical means for operating the X-ray tube with a rotary anode according to the present invention.

FIG. 3 is a partly sectional view of an X-ray tube with a rotary anode which is mounted in ball bearing on both sides of its anode.

FIG. 1 shows an X-ray tube 1 having a vacuum case, the end 2 of which directed toward the cathode consists of glass while the end 3 directed toward the anode consists of metal. The cathode 4 is introduced into the case in the usual manner and includes a shoulder 5 in which the glow cathode 5 is provided. The glow cathode 5 is supplied electrically by conduits 7 and 8. An electronic ray leaving the glow cathode 6 and symbolically indicated in FIG. 1 by the broken line 9, strikes the rotary anode l0 and produces there a bundle of X-rays indicated by broken lines as a cone 11. The anode 10 is connected by its axle 12 with the rotor 13 which is mounted by support 14 in ball bearings. The support 14 is soldered in a suitable opening of the base 15 of a metal case part 16 consisting of rust-free V2A steel. The part 16 is welded to the glass part 2 by means of a flange 19 molten with the glass case. In order to simplify the welding the flange is bent vertically outwardly relatively to the longitudinal axis of the tube, while the metal part l6'has the shape of a cup-like piece adapted to the rotor l3 and having a wall thickness of 0.5 to 1 mm. Its free end is bent outwardly so that the end of the bent part fits with the edge of the flange 17, as shown by the weld seam 18 in the drawing. The stator 19 used to drive the anode 10 is located outside of the metal part. As usual, it has four poles.

The operation of the tube takes place in a simple manner shown in FIG. 2. The connections 20 are connected with the net, so that the X-ray apparatus 21 supplies the corresponding electrical values. They are then transmitted on the one hand through the conduit 22 and on the other hand through the grounded conduit 23 as operational current to the tube 1. On the other hand the heating of the cathode 6 takes place through the heating current source 24, the current being transmitted to the cathode 6 through the conduit 7 and the conduit 25 connected with the conduit 8. By the one pole construction and the grounding of the anode it is possible to arrange the stator very closely, namely, directly on the outer side of the metal part 16. Furthermore, the rotor 13 can be also arranged very closely to the inner side of the metal part 16. The shortening of the distances provides a considerable improvement of the effectiveness of the stator and rotor, namely, of the drive.

However, it is also possible to operate the tube with the usual two pole drive. In that case, however, electrical insulation must be provided between the stator and the rotor, which can consist of a known insulated sleeve or of oil filling a space forming the known tube covermg.

FIG. 3 shows a different construction ofthe X-ray tube which includes a metal container 26 constituting the vacuum case. This case is pot-shaped and is closed by a plate 27, the edges of which are vacuum-tightly welded with the pot-like part 26, as indicated by the weld seam 28. The pot-like part 26 as well as the cover 27 are round, consist of refined steel sheets 1 mm thick and are provided at their center with a support for the anode 29. For that purpose the base of the pot-like part 26 as well as the central portion of the cover 27 are provided with recesses 30 and 31, respectively. These recesses contain a bearing 32 and a rotor 33. The drawing shows these parts only in the sectioned location of the recess 31. Only the rotor 34 is illustrated in therecess 30. Outside of the recesses 30 and 31 are located stators 34 and 35 used to drive the anode. An extension 36 is provided in a side wall of the pot-like part 26 for producing X-rays. Within the extension 36 is a cover 37 enclosing a glow cathode 38 which at locations 39 and 40 is connected with insulated lines introduced into the case. The rotary anode 29 itself consists of a conical part at the periphery of which an X-ray bundle 41 is produced which can pass outwardly through the cover 27.

The tube is operated in the above indicated manner in that an apparatus corresponding to the apparatus 21 of FIG. 2 provides high voltage to the tube on the one hand through the line 42 and on the other hand through the grounded line. The heating voltage from a source corresponding to the source 24 of FIG. 2 is provided between the lines 42 and 44. The operation is the same as that of the tube of FIG. 1.

The tube of FIG. 3 can also have a two pole operation. In that case it is also necessary to provide an elecmotor having a stator and a rotor connected with said anode for rotating said anode, and a case, said anode,

trically insulating device between the stators 34 and 35 said cathode and said rotor being located within said case, said stator being located outside of said case, said case having a portion located between said rotor and said stator consisting of metal which is a poor conductor of electrical current.

2. An X-ray tube according to claim 1, wherein said case has a portion consisting of glass which carries said cathode and encloses said anode, and a pot-like portion consisting of metal and enclosing said rotor.

3. An X-ray tube according to claim 2, wherein said glass portion has a flange welded to the metal portion.

4. An X-ray tube according to claim I, wherein said metal is rust-free steel.

5. An X-ray tube according to claim 1, wherein said anode has an axle, and bearings supporting said axle at opposite ends, each of said bearings having a separate rotor, the portion of the case enclosing the rotors consisting of metal of poor electrical conductivity. 

1. An X-ray tube, comprising an anode, a cathode, a motor having a stator and a rotor connected with said anode for rotating said anode, and a case, said anode, said cathode and said rotor being located within said case, said stator being located outside of said case, said case having a portion located between said rotor and said stator consisting of metal which is a poor conductor of electrical current.
 2. An X-ray tube according to claim 1, wherein said case has a portion consisting of glass which carries said cathode and encloses said anode, and a pot-like portion consisting of metal and enclosing said rotor.
 3. An X-ray tube according to claim 2, wherein said glass portion has a flange welded to the metal portion.
 4. An X-ray tube according to claim 1, wherein said metal is rust-free steel.
 5. An X-ray tube according to claim 1, wherein said anode has an axle, and bearings supporting said axle at opposite ends, each of said bearings having a separate rotor, the portion of the case enclosing the rotors consisting of metal of poor electrical conductivity. 